U.S. patent number 4,097,388 [Application Number 05/731,483] was granted by the patent office on 1978-06-27 for linear fluorinated polyether lubricant compositions containing perfluoroalkylether substituted phosphines.
This patent grant is currently assigned to The United States of America as represented by the Secretary of the Air. Invention is credited to Carl E. Snyder, Jr., Christ Tamborski.
United States Patent |
4,097,388 |
Snyder, Jr. , et
al. |
* June 27, 1978 |
**Please see images for:
( Certificate of Correction ) ** |
Linear fluorinated polyether lubricant compositions containing
perfluoroalkylether substituted phosphines
Abstract
A lubricant composition comprising (1) a base fluid having the
following formula: wherein R.sub.f is a perfluoroalkyl group, m and
n are integers whose sum is between 2 and 200 and the ratio of n to
m is between 0.1 and 10; and (2) a minor amount of a
perfluoroalkylether substituted aryl phosphine.
Inventors: |
Snyder, Jr.; Carl E. (Trotwood,
OH), Tamborski; Christ (Dayton, OH) |
Assignee: |
The United States of America as
represented by the Secretary of the Air (Washington,
DC)
|
[*] Notice: |
The portion of the term of this patent
subsequent to March 8, 1993 has been disclaimed. |
Family
ID: |
24939695 |
Appl.
No.: |
05/731,483 |
Filed: |
October 12, 1976 |
Current U.S.
Class: |
508/564;
508/582 |
Current CPC
Class: |
C10M
107/38 (20130101); C10M 137/12 (20130101); C10M
169/04 (20130101); C10M 2213/06 (20130101); C10N
2040/135 (20200501); C10N 2050/10 (20130101); C10M
2213/043 (20130101); C10M 2213/023 (20130101); C10M
2223/061 (20130101); C10N 2040/12 (20130101); C10M
2223/06 (20130101); C10M 2213/0623 (20130101); C10N
2040/13 (20130101); C10M 2213/04 (20130101); C10M
2213/0606 (20130101); C10N 2030/08 (20130101); C10N
2040/08 (20130101); C10M 2213/00 (20130101) |
Current International
Class: |
C10M
169/00 (20060101); C10M 169/04 (20060101); C10M
001/10 () |
Field of
Search: |
;252/49.9 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gantz; Delbert E.
Assistant Examiner: Metz; Andrew H.
Attorney, Agent or Firm: Rusz; Joseph E. Kuhn; Cedric H.
Government Interests
RIGHTS OF THE GOVERNMENT
The invention described herein may be manufactured and used by or
for the Government of the United States for all governmental
purposes without the payment of any royalty.
Claims
We claim:
1. A lubricant composition comprising (1) a base fluid consisting
essentially of a mixture of linear fluorinated polyethers having
the following formula:
wherein R.sub.f is CF.sub.3 or C.sub.2 F.sub.5, m and n are
integers whose sum is between 2 and 200 and the ratio of n to m is
between 0.1 and 10; and (2) a corrosion-inhibiting amount of a
perfluoroalkylether substituted aryl phosphine having the following
formula: ##STR7## wherein one of the R's is a perfluoroalkylether
group, two of the R's are fluorine, and n is 1, 2 or 3.
2. The lubricant composition according to claim 1 in which the
amount of the phosphine ranges from about 0.05 to 5 weight percent,
based upon the weight of the base fluid.
3. The lubricant composition according to claim 1 in which the
amount of the phosphine ranges from about 0.5 to 2.0 weight percent
based upon the weight of the base fluid.
4. The lubricant composition according to claim 1 in which one of
the R's of the phosphine is ##STR8## where x, y and z are zero or
an integer from 1 to 20, inclusive.
5. The lubricant composition according to claim 4 in which the
phosphine has the following formula: ##STR9##
6. The composition according to claim 4 in which the phosphine has
the following formula: ##STR10##
7. The lubricant composition according to claim 4 in which
phosphine has the following formula: ##STR11##
8. The lubricant composition according to claim 4 in which the
phosphine has the following formula: ##STR12##
9. The lubricant composition according to claim 4 in which the
phosphine has the following formula: ##STR13##
Description
BACKGROUND OF THE INVENTION
Because of their thermal stability, perfluorinated polyalkylether
fluids have a great potential for use as engine oils, hydraulic
fluids and greases. However, a serious drawback in their use
results from the fact that certain metals, e.g., certain ones
present in aircraft engine components, are corroded at elevated
temperatures in an oxidative environment. For example, when the
fluids are utilized as lubricants for mechanical components
composed of mild steels, serious corrosion has occurred at
temperatures of from 550.degree. to 600.degree. F. Furthermore,
stainless steels, titanium and titanium alloys are attacked by the
fluids at a temperature of about 600.degree. F. Moreover, when used
with titanium and titanium alloys, the fluids themselves undergo
negative viscosity changes to the detriment of continued
lubricating capacity.
An ideal lubricant composition would be one having a relatively
constant viscosity such that it is flowable or pumpable over a wide
temperature range, e.g., from -50.degree. F to 600.degree. F. Up to
the present time, a base fluid fulfilling this requirement has not
been available. For example, base fluids having a satisfactory
viscosity at low temperatures may degrade at elevated temperatures.
And base fluids which are stable and have a satisfactory viscosity
at elevated temperatures may be too viscous to flow or pump at
sub-zero temperatures. As a result, it has been necessary to make
compromises in the selection of base fluids dependent upon the use
conditions to be encountered. Such a procedure has not proven to be
entirely satisfactory.
In U.S. Pat. No. 3,393,151, issued to one of us as a coinventor on
July 16, 1968, lubricants are disclosed that comprise a
perfluorinated aliphatic polyether and a perfluorophenyl phosphorus
compound. In U.S. Pat. No. 3,499,041, issued to one of us on Mar.
3, 1970, certain perfluoroarylphosphines are disclosed as being
anti-corrosion additives for perfluorinated fluids. While the
phosphorus compounds described in these patents exhibit corrosion
inhibiting properties, at low temperatures they are only poorly
soluble in perfluorinated fluids. Also, certain members of the
classes of phosphorus compounds possess high volatility
characteristics for long term high temperature applications.
Because of these limitations, perfluorinated fluids containing such
anti-corrosion additives are not completely satisfactory for use in
long term, wide temperature range applications.
It is an object of this invention, therefore, to provide a
lubricant composition which has little if any corrosive effect upon
ferrous and titanium alloys.
Another object of the invention is to provide a lubricant
composition which has a relatively constant viscosity over a wide
temperature range.
A further object of the invention is to provide a lubricant
composition which undergoes substantially no degradation when
exposed to titanium.
Other objects and advantages of the invention will be apparent to
those skilled in the art upon consideration of the accompanying
disclosure and the drawing which shows graphically the
viscosity-temperature relationship of base fluids used in the
lubricant composition of this invention.
SUMMARY OF THE INVENTION
The present invention resides in a lubricant composition comprising
(1) a base fluid consisting essentially of a mixture of linear
fluorinated polyethers having the following formula:
wherein R.sub.f is CF.sub.3 or C.sub.2 F.sub.5, m and n are
integers whose sum is between 2 and 200 and the ratio of n to m is
between 0.1 and 10; and (2) a corrosion-inhibiting amount of a
perfluoroalkylether substituted aryl phosphine (fluorinated
phosphine) having the following formula: ##STR1## wherein one of
the R's is a perfluoroalkylether group (CF.sub.2 R.sub.f OR.sub.f),
two of the R's are fluorine, and n is 1, 2 or 3.
The base fluids (formula A) are synthesized by initially preparing
linear perfluorinated copolyethers by photochemical reaction with
molecular oxygen of a liquid phase consisting of a solution of
perfluoroethylene in an inert solvent. Elimination of the peroxidic
groups of the copolyethers by thermal treatment at a temperature
ranging from 100.degree. to 250.degree. C provides the base fluids
used in the lubricant composition of this invention.
The (CF.sub.2 CF.sub.2 O).sub.m and the (CF.sub.2 O).sub.n groups
of the fluorinated polyethers are randomly distributed in the
polyether molecules which have CF.sub.3 or C.sub.2 F.sub.5 end
groups. The molecules may also contain a small number, e.g., about
1 to 2 percent of the (CF.sub.2 CF.sub.2 O).sub.m and (CF.sub.2
O).sub.n groups, of (CF.sub.2).sub.3 O and (CF.sub.2).sub.4 O
groups. As mentioned above, m and n are integers whose sum is
between 2 and 200. The integers m and n can also be defined as
having values such that the fluorinated polyethers have a kinematic
viscosity ranging from about 15 to 1000 centistokes at 100.degree.
F as determined by the method of ASTM D445. The fluorinated
polyethers are normally obtained as mixtures of different
molecules, each of which has a well defined molecular weight. The
usual practice is to fractionate the fluorinated polyethers so as
to obtain a product having a desired average molecular weight or
kinematic viscosity as defined hereinabove. For a more complete
discussion of the fluorinated polyethers and the process for their
production reference may be made to U.S. Pat. No. 3,715,378, issued
to D. Sianesi et al. on Feb. 6, 1973, and to D. Dianesi et al., La
Chimica E L'Industria, 55, 202-221 (1973).
The preferred fluorinated phosphines (formula B) are those in which
the perfluoroalkylether group is para to the phosphorus atom. In
general, R can be any perfluoroalkylether group as long as the
group contains at least one ether linkage. However, it is often
preferred that the group contain two or more ether linkages.
Examples of perfluoroalkylether groups include the following where
R equals (CF.sub.2 R.sub.f OR.sub.f) and may be: ##STR2## where x,
y and z are zero or an integer from 1 to 20, inclusive, preferably
an integer from 1 to 4, inclusive.
The procedure followed in preparing completely fluorinated
phosphines, i.e., when n in the above formula equals 3, can be
represented by the following equations: ##STR3##
As seen from equation (1), 1,4-dibromotetrafluorobenzene is reacted
with ethylmagnesium bromide. The reaction is carried out by mixing
solutions of the compounds in suitable solvents under conditions
such as to form compounds (II), e.g., at about -5.degree. to
5.degree. C for about 15 minutes to 1 hour. Thereafter, a cuprous
chloride, bromide or iodide is added to the reaction mixture whose
temperature is allowed to rise to room temperature. The cuprous
halide reacts with compound (II), thereby forming organocopper
compound (III).
The organocopper compound (III) is an intermediate which can react
with perfluoroacyl halides to yield a variety of ketones. The
reaction that occurs is shown by equation (2). In carrying out the
indicated reaction, the perfluoroacyl halide (IV) is added to
organocopper compound (III) which has been cooled to about
-5.degree. to 5.degree. C. The compounds are usually allowed to
react at room temperature for a period of about 12 to 14 hours
after which the reaction mixture is hydrolyzed. After extracting
the mixture with a solvent for the ketone product (V), the solvent
layer is phase separated and dried. The ketone is then recovered by
fractional distillation.
As shown by equation (3), the ketone is fluorinated by reacting
same with sulfur tetrafluoride. The reaction is accomplished by
adding anhydrous hydrogen fluoride and sulfur tetrafluoride to a
cooled pressure vessel containing the ketone. The sealed pressure
vessel is then rocked and maintained at a temperature ranging from
about 150.degree. to 200.degree. C for a period of about 12 to 24
hours. After cooling and venting the vessel, its contents are
washed with a solvent. The solvent is then evaporated, and the
residue is fractionally distilled to yield fluorinated product
(VI).
In accordance with equation (4), butyllithium is added to a
solution of perfluoroalkylether compound (VI) at -70.degree. to
-80.degree. C. In the reaction that ensues, which generally takes
from 15 minutes to 1 hour, the bromine atom of compound (VI) is
replaced with a lithium atom, thereby forming perfluorinated
compound (VII). At the end of the reaction period, a solution of
phosphorus trichloride is added to compound (VII), and the reaction
that occurs yields a phosphine compound (VIII) of this invention.
In the reaction as depicted by equation (5), the reaction mixture
is stirred at about -70.degree. to -80.degree. C for about 0.5 to
1.5 hours after which it is allowed to warm slowly to about
-25.degree. to -35.degree. C over a period of about 3 to 10 hours.
Recovery of the product is accomplished by adding dilute
hydrochloric acid to the reaction mixture which is phase separated.
The bottom viscous layer is washed with water, diluted with a
fluorinated solvent and then dried. After filtration and removal of
solvent, phosphine product (VIII) is obtained by fractional
distillation in the form of a viscous liquid.
The materials used in preparing the intermediates and the phosphine
products are known compounds that are described in the literature.
The foregoing equations illustrate the preparation of para
substituted compounds. However, it is also within the scope of the
invention to use the meta and ortho isomers as anti-corrosion
additives in the lubricant composition. In synthesizing the meta
and ortho isomers, 1,3- and 1,2-dibromotetrafluorobenzene,
respectively, are utilized as a starting material rather than
1,4-dibromotetrafluorobenzene.
Any acyl halide can be used that corresponds to the formula R.sub.f
OR.sub.f C(O)X, where R.sub.f OR.sub.f is a perfluoroalkylether
group and X is a halogen. Examples of suitable acyl halides, which
are a source of the R.sub.f OR.sub.f groups, are disclosed in U.S.
Pat. Nos. 3,124,599, 3,214,478 and 3,721,696. Thus, depending upon
the acyl halide employed, a variety of ketones can be synthesized
according to the reaction illustrated by equation (2). As shown by
equation (3), the ketone is fluorinated with sulfur tetrafluoride
so that its ketone group becomes a CF.sub.2 group. Thus, in the
above formula defining the fluorinated phosphines as corrosion
inhibitors in the lubricant compositions of this invention, R
equals CF.sub.2 R.sub.f OR.sub.f where this group appears in the
foregoing equations.
The foregoing description has been concerned with completely
fluorinated phosphines. However, it is within the purview of the
present invention to use as the anti-corrosion additives partially
fluorinated phosphines, i.e., where n in the above formula is 1 or
2. The same procedure as described above is followed in preparing
the partially fluorinated phosphines except that in the reaction
illustrated by equation (5) phenyldichlorophosphine (n=2) or
diphenylchlorophosphine (n=1) is reacted with compound (VII)
instead of phosphorus trichloride. The reaction involved can be
represented by the following equation: ##STR4## In equation (6), n
equals 1 or 2.
A more detailed description of the synthesis of the fluorinated
phosphines is contained in our copending application Ser. No.
629,469, filed on Nov. 6, 1975 and now issued as U.S. Pat. No.
4,011,267. The disclosure of that application is incorporated
herein by reference.
In formulating the lubricant of this invention, a
corrosion-inhibiting amount of the phosphine compound is mixed with
the linear fluorinated polyether base fluid. The amount of the
phosphine compound used generally ranges from 0.05 to 5 weight
percent, preferably 0.5 to 2 weight percent, based upon the weight
of the base fluid.
The present invention provides a lubricant composition which is not
subject to the disadvantages of the prior art lubricants. The
outstanding properties of the lubricant can be attributed not only
to the particular base fluid and the phosphine additive used but
also to the unexpected effect obtained by mixing the two
components. Importantly, the phosphine anti-corrosion additives are
soluble at low temperatures in the base fluid and are substantially
non-volatile at elevated temperatures. As a result, there is
provided a lubricant containing an amount of anti-corrosion
additive that is adequate for long term applications at elevated
temperatures while still maintaining excellent formulation
stability after storage at low temperatures for long periods of
time.
Of equal importance, the base fluid possesses a relatively constant
viscosity over a wide temperature range. In the drawing there is
illustrated graphically the variation in kinematic viscosity over a
wide temperature range of three different base fluids as disclosed
herein. The data were obtained in accordance with the method of
ASTM D445. From an examination of the graphs, it is seen that the
change in kinematic viscosity is relatively small over a wide
temperature range. As a result, the base fluids under the test
conditions are flowable or pumpable over the temperature range.
However, it has also been found that the base fluid per se degrades
rapidly under use conditions at elevated temperatures.
Surprisingly, it was discovered that the phosphine additive
functions to oxidatively stabilize the base fluid at elevated
temperatures without affecting its desirable viscosity
characteristics. Thus, the lubricant composition of this invention
in addition to its other desirable properties has a relatively
constant viscosity such that it is flowable or pumpable over a wide
temperature range.
A more complete understanding of the invention can be obtained by
referring to the following illustrative examples which are not
intended, however, to be unduly limitative of the invention.
EXAMPLE I
A series of runs was conducted for the purpose of determining the
effectiveness of lubricant compositions of this invention.
Lubricant compositions were formulated by mixing (1) a base fluid
having the following formula:
where R.sub.f is CF.sub.3 or C.sub.2 F.sub.5, m and n are integers
having values such that the fluid has a kinematic viscosity of
about 17.8 centistokes at 100.degree. F with (2) various weight
percentages, based upon the weight of the base fluid, of a
fluorinated phosphine having the following formula: ##STR5## The
base fluid used was Fomblin Z fluid, a product of Montedison,
S.p.A., Milan, Italy.
In the runs a specimen of steel, titanium alloy or titanium was
immersed in the formulations that were prepared. The compositions
of the steel and titanium alloys are described in the literature.
For comparison purposes, runs were also carried out in which
specimens were immersed in polyether fluid which did not contain
the anti-corrosion additive. The materials were contained in an
oxidation test tube having a take-off adapter coupled to an air
entry tube. An aluminum block bath provided the means for heating
the test tube and an "overboard" test procedure (no reflux
condenser) was followed.
Air was bubbled through the formulations, or in the case of the
control test through the polyether fluid, at the rate of one liter
of air per hour for a period of 24 hours. The runs were conducted
at a constant temperature of 550.degree. F. The specimens as well
as the apparatus used were weighed prior to and after completion of
each run.
The data obtained in the runs are set forth below in the
tables.
TABLE I
__________________________________________________________________________
Weight Change, mg/cm.sup.2 Kinematic 52100 410 440C Viscosity Fluid
Bear- Stain- M-50 Stain- Wt % Change at Loss 4140 ing less Tool
less Additive 100.degree. F % Wt % Steel Steel Steel Steel Steel
__________________________________________________________________________
550.degree. F None (1) 83.75 +0.024 +0.48 -5.54 -2.37 -3.10 0.5
+3.99 0.57 -0.87 +0.51 +0.01 +0.68 +0.12 1.0 +0.22 0.31 +0.042
+0.031 +0.05 +0.01 0.00 2.0 +0.85 0.69 +1.22 +0.84 +0.13 +1.02
+0.16 600.degree. F None (1) 100 -3.54 +1.60 -8.58 +0.60 -9.89 0.5
0.0 0.53 -3.61 +1.38 -0.01 +2.25 -0.01 1.0 +0.1 0.25 +1.43 +0.41
-0.35 +0.44 -0.02 2.0 -0.22 0.45 +4.65 +0.46 0.00 +2.74 +0.01
__________________________________________________________________________
(1) Insufficient fluid to measure.
TABLE II
__________________________________________________________________________
Kinematic Viscosity Fluid Wt % Change at Loss Weight Change,
mg/cm.sup.2 Temp, .degree. F Additive 100.degree. F, % Wt %
Ti(6A14V) Ti(pure) Ti(4A14Mn)
__________________________________________________________________________
550 None -97.22 59.87 +0.06 -0.28 -0.28 550 0.5 +3.87 0.57 +0.06
0.00 +0.03 550 1.0 +0.16 0.10 +0.01 +0.01 +0.01 550 2.0 +0.39 0.17
+0.07 +0.05 +0.10
__________________________________________________________________________
EXAMPLE II
Runs are carried out in which lubricant compositions are tested by
the same procedure described in Example I. The lubricant
compositions are formulated by mixing the same base fluid used in
Example I with various weight percentages of several fluorinated
phosphine additives. The following fluorinated phosphines are used
in formulating the lubricants: ##STR6## The data obtained in the
runs are substantially the same as the data obtained in the runs of
Example I.
The data in the foregoing tables show that the lubricant
compositions of the invention have little if any corrosive effect
upon titanium and ferrous and titanium alloys. Also, there was
substantially no degradation of the lubricant compositions at the
elevated temperatures even though the base fluid per se was
severely degraded. It is thus seen that the phosphine additives
function both as an anti-corrosion and an anti-oxidation agent.
Because of their outstanding properties, the lubricants can be used
in applications requiring extreme temperature conditions. Examples
of uses for the lubricants include gas turbine engine lubricants,
nonflammable hydraulic fluids, greases compatible with liquid
oxygen, and liquid coolants and general purpose lubricants.
As will be evident to those skilled in the art, modifications of
the present invention can be made in view of the foregoing
disclosure without departing from the spirit and scope of the
invention.
* * * * *